---
title: "Troubleshooting common TYPO3 backend login problems"
manual: "Getting Started"
version: "main"
permalink: "https://docs.typo3.org/permalink/t3start:troubleshooting-backend-login@main"
source: "Troubleshooting/BackendLogin.rst"
modified: "2026-09-15T08:44:38+00:00"
---

# Troubleshooting common TYPO3 backend login problems

The following errors can happen during backend login:

-   [Login page reloads without error](https://docs.typo3.org/permalink/t3start:login-page-reloads-without-error@main)
-   ["Invalid Credentials" error](https://docs.typo3.org/permalink/t3start:invalid-credentials-error@main)
-   [White screen before or after login](https://docs.typo3.org/permalink/t3start:white-screen-before-or-after-login@main)
-   [Access denied before or after login](https://docs.typo3.org/permalink/t3start:access-denied-before-or-after-login@main)
-   ["Account locked" message](https://docs.typo3.org/permalink/t3start:account-locked-message@main)
-   ["Page Not Found" or 404 Error](https://docs.typo3.org/permalink/t3start:page-not-found-or-404-error@main)
-   [Broken login form or missing elements](https://docs.typo3.org/permalink/t3start:broken-login-form-or-missing-elements@main)

> [!TIP]
> [Creating a TYPO3 backend administrator](https://docs.typo3.org/permalink/t3start:backend-users-admin-creation@main)
> is a solution if you lost the password or user name of your administrator account.

## Login page reloads without error

-   Try deleting all browser cookies and caches or use a different browser /
    device. There might be an outdated cookie that prevents log-in.
-   Clear all TYPO3 caches via console command or install tool.
-   Delete folder `var/cache` to remove possible corrupted cache data.
-   Check the cookies configuration in TYPO3: Ensure that cookie-related
    settings ([sessionTimeout](https://docs.typo3.org/m/typo3/reference-coreapi/main/en-us/Configuration/Typo3ConfVars/BE.html#confval-globals-typo3-conf-vars-be-sessiontimeout),
    [cookieDomain](https://docs.typo3.org/m/typo3/reference-coreapi/main/en-us/Configuration/Typo3ConfVars/BE.html#confval-globals-typo3-conf-vars-be-cookiedomain))
    are correct and not causing session issues. Additionally, if
    [$GLOBALS\[TYPO3_CONF_VARS\]\[BE\]\[cookieSameSite\]](https://docs.typo3.org/m/typo3/reference-coreapi/main/en-us/Configuration/Typo3ConfVars/BE.html#confval-globals-typo3-conf-vars-be-cookiesamesite)
    is set to "none", a login will only work on HTTPS connections.

## "Invalid Credentials" error

-   Check if the username and password are correct.
-   Try to [Create a new backend administrator](https://docs.typo3.org/permalink/t3start:backend-users-admin-creation@main)
    and use that one.

## White screen before or after login

Many older TYPO3 files contain a line like the following that needs to be replaced:

```diff
-defined('TYPO3_MODE') or die();
+defined('TYPO3') or die();
```

The PHP constant `TYPO3_MODE` was removed with TYPO3 v12 but it is still
widespread in older code examples and extensions. This can also happen if you
installed a TYPO3 extension that is not compatible with newer TYPO3 versions.

If you have this line in your own code, replace it. If you find it in the above
code in a third party extension, check if a newer version is available. If you
do not find one you can try to reach out to the extension author or patch it
yourself.

## Access denied before or after login

-   If the line above contains "Access denied." or a similar string that string will
    be output and the login page contains nothing else:

    ```diff
    -defined('TYPO3_MODE') or die('Access denied.');
    +defined('TYPO3') or die('Access denied.');
    ```

    The solution is the same like for [White screen before or after login](https://docs.typo3.org/permalink/t3start:troubleshooting-login-white-screen@main).
-   Check file permissions on the TYPO3 files.
-   Check the `.htaccess` or Nginx configurations

## "Account locked" message

-   Wait the required time
-   Or delete the folder `var/cache`

## "Page Not Found" or 404 Error

-   Check file permissions on the TYPO3 files.
-   Check the `.htaccess` or Nginx configurations

## Broken login form or missing elements

-   Try deleting all browser cookies and caches or use a different browser /
    device. There might be an outdated cookie that prevents log-in.
-   Clear all TYPO3 caches via console command or install tool.
-   Was there a warning during `composer install`? The `_assets` folder
    might not have been properly symlinked during installation.
-   Check the browser console for errors.